Rotary drill bits employing polycrystalline diamond compact (“PDC”) cutters are often employed for drilling subterranean formations. Conventional PDC cutters may comprise a diamond table formed under ultra high temperature, ultra high pressure conditions onto a substrate, typically of cemented tungsten carbide. Conventional drill bit bodies may be formed of steel or may comprise a so-called tungsten carbide matrix including tungsten carbide particles distributed within a binder material.
Tungsten carbide matrix drill bit bodies may be fabricated by preparing a mold that embodies the inverse of the desired generally radially extending blades, cutting element sockets or pockets, junk slots, internal watercourses and passages for delivery of drilling fluid to the bit face, ridges, lands, and other external topographic features of the drill bit. Particulate tungsten carbide may then be placed into the mold and a binder material, such as a metal including copper and tin, may be melted into the tungsten carbide particulate and solidified to form the drill bit body. Steel drill bit bodies may be fabricated by machining a piece of steel to form generally radially extending blades, cutting element sockets or pockets, junk slots, internal watercourses and passages for delivery of drilling fluid to the bit face, ridges, lands, and other external topographic features of the drill bit.
In both matrix-type and steel bodied drill bits, a threaded pin connection may be formed for securing the drill bit body to the drive shaft of a downhole motor or directly to drill collars at the distal end of a drill string rotated at the surface by a rotary table, top drive, drilling motor or turbine.
Conventional cutting element retention systems or structures that have been employed generally comprise two different styles. One style includes tungsten carbide studs comprising a cylindrical tungsten carbide cylinder having a face oriented at an angle (back rake angle) with respect to the longitudinal axis of the cylinder, the face carrying a superabrasive cutting structure thereon. The cylinder may be press-fit or brazed into a recess formed in the bit that is generally oriented perpendicularly to the blades extending from the bit body on the bit face. A second type of retention system includes the brazed attachment of a generally cylindrical cutting element into a recess (e.g., a cutter pocket) formed on the bit face, typically on a blade extending from the bit face.
Generally speaking, the first cutting element retention style described above is designed for a stud type cutting element, while the second cutting element retention style described above is designed for generally cylindrical cutting elements, such as PDC cutters. In either system, the orientation of the cutting elements is conventionally held stationary relative to the bit body as the drill bit is used. Of the two different types of cutting element retention configurations utilized in the manufacture of rotary drill bits, cylindrical cutting elements are generally more common. Stud-type cutting elements, on the other hand, are relatively uncommon and may require a brazing or infiltration cycle to affix the PDC or TSPs to the stud.